'Operation Spark'), a Soviet military operation in January 1943 during World War II, aimed to break the Wehrmacht's siege of Leningrad.

[7] The success led to Operation Polyarnaya Zvezda less than two weeks later, which aimed to decisively defeat Army Group North and to lift the siege altogether.

The corridor remained within range of German artillery, and the Red Army did not finally lift the siege until a year later, on 27 January 1944.

By 8 September 1941, German and Finnish forces had surrounded the city, cutting off all supply routes to Leningrad and its suburbs.

[10] Despite the failures of earlier operations, lifting the siege of Leningrad was a very high priority, so new offensive preparations began in November 1942.

The Soviet forces were planning or conducting offensive operations across the entire front, especially in southwestern Russia.

Both factors greatly hindered the mobility of artillery and vehicles in the area, providing a considerable advantage to the defending forces.

Because the front line had changed very little since the blockade was established, German forces had built an extensive network of interconnected trenches and obstacles, interlocking artillery and mortar fire.

However, due to the reverse at Stalingrad and the Soviet offensive at Velikiye Luki to the south of Leningrad, Army Group North was ordered to go on the defensive and was stripped of many troops.

[15] At the start of the Soviet offensive, the German 18th Army, led by Georg Lindemann consisted of 26 divisions spread across a 450 km (280 mi) wide front.

The German divisions were well fortified in this area, where the front line had been virtually unchanged since September 1941, and hoping to repel the Soviet offensive.

Only a limited number of senior officers were involved in the planning, all redeployments took place in bad weather or at night and simulated attack preparations were made elsewhere to confuse the German side.

The Soviet attack started five minutes before the artillery preparation finished with a Katyusha barrage, to fully exploit its effects.

[24] The Volkhov Front attack saw less success as the forces of the 2nd Shock Army managed to envelop but not destroy the German strong points at Lipka and Workers Settlement No.

8 and Kruglaya Grove the advance was 1–2 km (0.62–1.24 mi) deep, while even further south, the flanking attacks by the 8th Army only managed to capture the first line of German trenches.

One improvised battle group consisting of five battalions from the 96th Infantry Division, supported by artillery and four Tiger tanks moved to Gorodok No.

[26] The German side, after their counterattacks had failed to throw back the Soviet troops, started further reinforcing the area by assembling battle groups using portions of divisions from the quiet parts of the front.

[27] On 14 January the weather improved enough to allow air support again and the Soviet advance resumed, albeit at a slow pace.

To speed up the encirclement of the strong point at Lipka, the Soviet side used the 12th Ski Brigade which crossed the ice of the Ladoga Lake and attacked the German rear lines.

[31] Group Huhner became cut off too and was ordered to break out through the forested area toward Siniavino before the main Soviet forces arrived and made a breakout impossible.

Group Huhner abandoned its artillery and heavy equipment[28] and ran "the gauntlet of fire" before reaching Siniavino on 19 January.

The Soviet forces were unable to advance any further, and instead started fortifying the area to thwart any German attempt at re-establishing the blockade.

On 21 January, work started on the rail line linking Leningrad to the rest of the country through the captured corridor.

The plan from the State Defense Committee written on 18 January, ordered the construction to be finished in 20 days.

[8] Breaking the blockade also had a significant strategic effect, although that was overshadowed by the surrender of the German 6th Army at Stalingrad only a few days later.

Lacking sufficient reinforcements, the command of Army Group North made the decision to shorten the front line by evacuating the Demyansk Pocket salient.

This much more ambitious offensive operation aimed to decisively defeat Army Group North, but faltered early on.

[8] The Soviet forces carried out several other offensives in the area in 1943, slowly expanding the corridor, making other small gains before finally capturing Siniavino in September.